Device and method for drying an air stream

ABSTRACT

A device for dehumidifying an air stream includes at least one first module including at least one Peltier element and at least one second module including at least one Peltier element. The entirety of the first module forms a first zone for cooling the air stream. The entirety of the second module forms a second zone for dehumidifying the air stream. The entirety of the first and the second modules forms an air channel for the air stream. A water discharge channel is disposed below the entirety of the second module and receives water accumulating during the dehumidifying of the air stream in the second zone. At least one sensor for measuring a temperature and/or a moisture of the air stream provides at least one output signal. A control unit including at least one controller controls the Peltier elements based on the at least one output signal of the at least one sensor.

TECHNICAL FIELD

The invention relates to a device and a method for dehumidifying an air stream.

Such a device can be used in an air conditioner to dehumidify one or a plurality of air streams circulating in such a device. An air conditioning system should also be understood by the term air conditioner.

BRIEF DESCRIPTION OF THE INVENTION

It is the object of the invention to develop a device for dehumidifying an air stream, whose operation is as energy-efficient as possible.

The said object is solved according to the invention by the features of claims 1 and 5. Advantageous embodiments are obtained from the dependent claims.

A device for dehumidifying an air stream comprises an air channel having an inlet through which the air to be dehumidified is supplied and having an outlet through which the dehumidified air is released. According to the invention, the air channel is divided into at least two zones, wherein a temperature in the first zone can be controlled in such a manner that the air stream at the end of the first zone is cooled to a dew point temperature corresponding to the air stream or to a temperature which is higher than the dew point temperature by a small amount and wherein a temperature in the second zone can be controlled in such a manner that the air stream in the second zone releases moisture in the form of water.

The material and/or the surface structure of the walls defining the air channel are preferably configured differently in the first zone and in the second zone.

The air channel is, for example, divided into at least four zones, wherein a temperature in the third zone can be controlled in such a manner that the air stream in the third zone releases moisture in the form of water and wherein waste heat accumulating in the third zone is supplied to the air stream in the fourth zone.

The temperature in the third zone is preferably controlled by means of at least one Peltier element, whose cold side during operation cools the third zone and whose warm side during operation heats the fourth zone.

The temperature of the walls of the air channel is preferably controlled by means of Peltier elements, which are controlled by a control unit comprising at least two controllers, wherein the first controller controls the Peltier element or the Peltier elements of the first zone in such a manner that the air stream in the first zone is cooled without condensing water and wherein the second controller controls the Peltier element or the Peltier elements of the second zone in such a manner that the air stream releases water in the second zone.

The method according to the invention for dehumidifying an air stream accordingly comprises the steps:

a) making the air stream flow through a first zone in which the air stream is cooled to such an extent that its temperature at the end of the zone reaches a value which corresponds to the dew point temperature or is higher than the dew point temperature by a small amount, and b) making the air stream flow through a second zone in which the air stream is cooled to such an extent that water condenses. In order to achieve this, the temperature of the walls of the first zone must be higher than the dew point temperature of the air stream, which is associated with its current temperature and current relative humidity, whereas the temperature of the walls of the second zone must lie below the “local” dew point temperature of the air stream. In this context, it should be noted that the dew point temperature of the air stream decreases along the second zone because the air stream condenses moisture in the form of water. The dew point temperature in the second zone is location-dependent and is therefore designated as “local” dew point temperature.

The method advantageously comprises the additional step of making the air stream flow through a third zone which is cooled to or below the local dew point temperature so that water condenses, and then making the air stream flow through a fourth zone in which the air stream is heated by the heat accumulating in the third zone.

The invention is explained in detail hereinafter with reference to an exemplary embodiment and with reference to the drawings. The figures are schematic and are not drawn to scale.

DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic diagram which illustrates both the structure of a device according to the invention for dehumidifying an air stream and also a method according to the invention for dehumidifying an air stream,

FIG. 2 shows a Mollier diagram,

FIG. 3 shows an enlarged section of the Mollier diagram from FIG. 2 and an example of a dehumidification process,

FIG. 4 shows in perspective schematic view an exemplary embodiment of a device for dehumidifying an air stream,

FIG. 5 shows individual parts of a first module,

FIG. 6 shows details of the first module in side view,

FIG. 7 shows the first module in perspective view,

FIG. 8 shows individual parts of a second module,

FIG. 9 shows the second module in perspective view,

FIG. 10 shows an individual part of the second module in another embodiment, and

FIG. 11 shows a circuit diagram for controlling the device from FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic diagram which illustrates the structure of a device according to the invention for dehumidifying an air stream on the one hand and a method according to the invention for dehumidifying an air stream on the other hand. The device comprises an air channel having an inlet 1 through which the air to be dehumidified is supplied and having an outlet 2 through which the dehumidified air is released. The air stream is shown by an arrow 3. The air channel is either divided into two zones 4 and 5 or, as shown, into four zones 4, 5, 6A, and 6B, wherein the zones are either directly adjacent to one another or are somewhat spaced apart from one another. The first zone 4 is used to cool the supplied air stream, wherein the air stream at the end of the first zone 4 is cooled to the dew point temperature or to a temperature which is higher than the dew point temperature by a small amount. The dew point temperature is that temperature of the moist air at which this is saturated with water vapor so that in the event of a further lowering of temperature, water would condense. The dew point temperature is therefore that temperature of moist air at which the relative air humidity, phi, is 100 percent. In the first zone 4 the air is consequently cooled predominantly without water condensing. It is possible that at the end of the first zone 4, some water has already condensed without this disturbing the operation. This is the case, for example, when the temperature is below the dew point temperature, which naturally can occur since the temperature must be regulated. The second zone 5 is used to further cool and dehumidify the air stream, i.e. to extract moisture from the air stream and condense this in the form of water. The water passes into a water discharge channel. The temperature in the second zone 5 must therefore be below the local dew point temperature of the air stream everywhere. The third zone 6A and the fourth zone 6B are optional and serve to heat the cold dehumidified air stream efficiently to a desired temperature. Whether these two zones are used or not depends on the operating mode of the air conditioner.

The device is additionally equipped with at least one sensor in order to operate said device in accordance with the method according to the invention described hereinafter. The at least one sensor is used to measure the temperature and/or the relative humidity of the air stream.

The method according to the invention for dehumidifying an air stream accordingly comprises the steps

a) making the air stream flow through a first zone 4 in which the air stream is cooled to such an extent that its temperature at the end of the zone 4 reaches a value which corresponds to the dew point temperature or is higher than the dew point temperature by a small amount, b) making the air stream flow through a second zone 5 in which the air stream is cooled to such an extent that water condenses, and c) optionally making the air stream flow through a third zone 6A which is cooled to or below the local dew point temperature so that water condenses, and then making the air stream flow through a fourth zone 6B in which the air stream is heated by the heat accumulating in the third zone 6A.

In this context, the following should be noted:

the dew point temperature of the air depends on various factors, in particular on the temperature of the air, the water content of the air, and the pressure of the air. The relative humidity phi, given in %, designates the ratio of the instantaneous water vapor content in the air to the maximum possible water vapor content at the same temperature.

The dew point temperature in zones 5 and 6A decreases along the zones since water condenses in these zones, which means that the water content of the air stream and therefore the relative humidity phi decrease continuously.

The dew point temperature of the air stream at any position in zones 5 and 6A can be determined, for example, by measuring the temperature and the relative humidity phi of the air stream by means of sensors and then determining the associated dew point temperature. The dew point temperature T_(p1) can be determined, for example, by calculations using the equation

$\begin{matrix} {T_{p\; 1} = \frac{{241.2*{\ln \left( \frac{phi}{100} \right)}} + \frac{4222.03716*T}{241.2 + T}}{17.5043 - {\ln \left( \frac{phi}{100} \right)} - \frac{17.5043*T}{241.2 + T}}} & (1) \end{matrix}$

where the dimensional unit of the temperatures T and T_(p1) is degrees Celsius and the relative air humidity phi should be inserted in percent. The dew point temperature T_(p1) can, however, also be determined by means of a Mollier diagram.

The Mollier diagram is also suitable for representing the dehumidification process of the air stream and deducing from this how the temperature should be regulated in zones 4 and 5 or 4, 5, and 6A. FIG. 2 shows a Mollier diagram. The diagram contains a family of curves which represent the behavior of the dew point temperature T_(p1) as a function of the water content X and the temperature T of the air for various values of the relative air humidity phi. The dehumidification process is explained in detail hereinafter with reference to an example having randomly selected values of the temperature T and the relative humidity of the air stream by reference to FIG. 3 which shows an enlarged section of the Mollier diagram from FIG. 2. The process of dehumidifying the air stream is shown by four arrows, which adjoin one another. One of the zones 4, 5, 6A, and 6B of the device for dehumidifying the air stream is associated with each of the four arrows. On entry of the air stream into the first zone 4, i.e. at the inlet 1, the air stream in this example has a temperature T=30° and a relative air humidity phi=50%. On leaving the zone 6B, i.e. at the outlet 2 of the device for dehumidifying the air stream, the air stream in this example should have reached a temperature T=22° and a relative air humidity phi=30%. In the first zone 4 the air stream is only cooled without water being separated. The first arrow therefore runs perpendicularly and points downward. In the first zone 4 the air stream must be cooled to a temperature T₁, which approximately corresponds to its dew point temperature, T_(p1), of T_(p1)=18.5° C. in the example. If no water is to be condensed in the first zone 4, the temperature T₁ must lie above the dew point temperature T_(p1). If, however, water may be condensed in the first zone 4, in particular in the region of the end of the first zone 4, the temperature T₁ of the air stream in the region of the end of the first zone 4 may then also reach a value lying below the dew point temperature T_(p1). In the second zone 5, the air stream is continuously dehumidified. Since it thereby loses water, the dew point temperature diminishes continuously along the second zone 5, as is clearly apparent in the Mollier diagram. In the third zone 6A, the air stream is also continuously dehumidified, consequently the dew point temperature also diminishes continuously along the third zone 6A. In the example, the air stream must have reached the temperature T₂=3.5° C. at the end of the third zone 6A. In the fourth zone 6B, the air stream is heated to the desired temperature of 22° C. in the example, where it then also reaches the desired relative air humidity phi=30%.

The two zones 6A and 6B are coupled to one another in such a manner that the heat accumulating in zone 6A and to be removed, is supplied to zone 6B to heat the air stream to the desired temperature. The dew point temperature at the transition from the second zone 5 to the third zone 6A should be adjusted or regulated in accordance with this requirement.

The invention relates in its main aspect to the cooling and dehumidification of an air stream, wherein the cooling takes place in the first zone 4, in which no water is yet condensed from the air stream, wherein the relative air humidity on leaving the first zone 4 is ideally approximately 100%, and wherein the dehumidification only takes place in the subsequent second zone 5. This division makes it possible to optimize the material and the surface structure of the walls of the air channel defining the first zone 4 for optimal heat transfer without condensation, and to optimize the material and the surface structure of the walls of the air channel defining the second zone 5 for optimal heat transfer with condensate or droplet formation and rapid drainage of the condensed water. It is optimal if a monolayer of water forms on the walls of the second zone 5 since such an extremely thin layer on the one hand effects the rapid drainage of the water and on the other hand offers only a low heat resistance. A possible embodiment of the walls of the second zone 5 is that they are coated with a material having a fraction of hydrophobic and hydrophilic effect which varies from top to bottom in the direction of gravity, wherein the hydrophobic fraction predominates in the upper region and the hydrophilic fraction predominates in the lower region.

When the air flow leaves the second zone 5, it is cold and relatively dry. It can now be supplied, for example, directly to a room to be air conditioned or mixed with fresh air and supplied to the room or mixed with exhaust air removed from the room and returned to the room, or heated and supplied to the room as prepared supply air. The invention relates in a further aspect to a device in which the air channel is divided into at least four zones 4, 5, 6A, and 6B, wherein a temperature in the third zone 6A can be controlled in such a manner that the air stream in the third zone 6A releases moisture as water and wherein waste heat accumulating in the third zone 6A is supplied to the air stream in the fourth zone 6B. This is advantageously accomplished by means of at least one Peltier element which is used such that on the one hand, its cold side cools the walls of the third zone 6A to the required temperature and on the other hand, its warm side heats the walls of the fourth zone 6B.

FIG. 4 shows a possible exemplary embodiment of a device for dehumidifying an air stream. The first zone 4 is formed by at least one module 7 of a first type, in the example, two modules 7 are disposed consecutively. The second zone 5 is formed by at least one module 8 of a second type, in the example, five modules 8 are disposed consecutively. The modules 7 and 8 have a similar structure and only differ in certain details.

FIG. 5 shows the individual parts of which the module 7 is composed. These individual parts are a frame 10, a first perforated plate 11, a second perforated plate 12, a Peltier element 13, and a cooling element 14. The frame 10, the first perforated plate 10, and the second perforated plate 12 have the same outer contour. The perforated plates 11 and 12 contain a plurality of holes, which in the example are circular. The holes of the first perforated plate 11 are disposed in an offset manner with respect to the holes of the second perforated plate 12. A plurality of frames 10, first perforated plates 11, and second perforated plates 12 are connected to one another in the sequence frame 10, first perforated plate 11, frame 10, second perforated plate 12, frame 10, first perforated plate 11, frame 10, second perforated plate 12, etc., so that they form a channel for the air stream. FIG. 6 illustrates this structure: it shows in side view the frames 10, first perforated plates 11, and second perforated plates 12, wherein FIG. 6 was stretched in the horizontal direction so that the individual parts can be better identified. FIG. 7 shows the module 7 in perspective view. In this example, six Peltier elements 13 are mounted on each side wall 16 of the channel, of which two are shown in FIG. 6. The channel has a base 15, two side walls 16, and a cover 17. At least one Peltier element 13 is mounted on at least one of the two side walls 16, preferably on both side walls 16. During operation of the module 7, a current flows through the Peltier elements 13, which cools the side of the Peltier elements 13 facing the channel and heats the side of the Peltier elements 13 facing away from the channel. This heat must be removed to the surroundings. This can be accomplished in various ways, for example, by air cooling or water cooling. In the example, a cooling element 14 is mounted on the Peltier elements 13, which is cooled with water or another medium which circulates in a circuit and releases the heat absorbed by the Peltier elements 13 to the surroundings at a suitable point. In the example shown in FIG. 7, six Peltier elements 13 and two cooling elements 14 (of which one is omitted) are mounted on each side wall of the channel.

The perforated plates 11 and 12 are flow obstacles which are disposed transversely to the direction of the air stream or the channel. The air flowing through the channel either impinges on the perforated plate or flows unhindered through the holes of the perforated plate. Since the holes of the first perforated plates 11 are disposed in an offset manner with respect to the holes of the second perforated plates 12, the air is continuously deflected inside the channel of the module 7 so that it continuously comes in contact with the perforated plates and thereby cools.

FIG. 8 shows the individual parts of which the module 8 is composed. These individual parts are the frame 10, a certain number of different plates with tips, in this example, four different plates, i.e. a first sawtooth plate 18, a second sawtooth plate 19, a third sawtooth plate 20, a fourth sawtooth plate 21, the Peltier element 13, and the cooling element 14. FIG. 9 shows the module 8 in perspective view. A plurality of frames 10, first sawtooth plates 18, second sawtooth plates 19, third sawtooth plates 20, and fourth sawtooth plates 21 are connected to one another in the sequence frame 10, first sawtooth plate 18, frame 10, second sawtooth plate 19, frame 10, third sawtooth plate 20, frame 10, fourth sawtooth plate 21, frame 10, first sawtooth plate 18, frame 10, second sawtooth plate 19, frame 10, third sawtooth plate 20, frame 10, fourth sawtooth plate 21, etc. so that they form a channel for the air stream. The frame 10 and the four sawtooth plates 18 to 21 per se have the same external contour but the sawtooth plates 18 to 21 are open at the bottom, i.e. on the side facing the base 15 of the channel so that the base 15 of the channel of the assembled module 8 contains a plurality of slots, which are each formed between neighboring frames 10. The sawtooth plates 18 to 21 comprises a surface 22, whose edge 23 facing the base 15 of the channel of the module is provided with tips and typically is configured in a sawtooth form. Peltier elements 13 and cooling elements 14 are mounted in the same way as in the module 7. The three sawtooth plates 18 to 21 differ in respect of the distance at which the surface 22 is disposed from the base of the channel of the module 8.

The sawtooth plates 18 to 21 are flow obstacles which are disposed transversely to the direction of the air stream or the channel of the module 8. The air flowing through the channel of the module 8 impinges on the surface 22, whereby moisture contained in the air condenses in the form of water on the surface 22 and flows downward as a result of gravity, accumulates at the tips of the edge 23, becomes detached there, drops downward, and passes through the slots in the base of the channel of the module 8 into the water discharge channel 9 mounted in the zone 5 underneath the module 8 (FIG. 4). The water discharge channel 9 is sealed with respect to the surroundings. The water discharge channel 9 has an opening through which the water passes preferably by means of a siphon or a long thin tube with correspondingly great friction in order to prevent air flowing through the air channel from being able to escape into the surroundings through the slots in the base 15 of the channel and the opening in the water discharge channel 9. In the example, the water discharge channel 9 extends over all three zones 4 to 6A.

In this example, the frames 10, perforated plates 11, 12, and sawtooth plates 18, 19, 20 are provided with holes so that these can be screwed together by means of screws to the module 7 or 8 or also to the entire air channel. The frames 10, perforated plates 11, 12, and sawtooth plates 18, 19, 20 consist of a very good heat-conducting material. The lower the thermal conductivity, the thicker are these frames and plates. The Peltier elements 13 are mounted on the outer wall of the channel formed by the frames 10 and perforated plates 11, 12 or frame 10 and sawtooth plates 18 to 21 and consequently are in thermal communication with the perforated plates 11, 12 and sawtooth plates 18 to 21 to be cooled. The cooling elements 14 are mounted on the Peltier elements 13.

The third zone 6A of the device according to the invention for dehumidifying an air stream is, as has already been mentioned, optional. Said zone also comprises modules 8 of the second type and is configured in such a manner that the air stream flows through the inside of these modules 8 and then in a channel formed on the outside of the modules 8 flows past the warm sides of the Peltier elements 13 of these modules 8 and is thereby heated. The inside of the modules 8 forms the third zone 6A which is not visible in FIG. 4, the outside of the modules 8 forms the fourth zone 6B.

The modules 7 and 8 can also be constructed in a different manner. An example of a different design is illustrated in FIG. 10 by reference to the sawtooth plate 19. The sawtooth plate 19 here consists of two different materials, i.e. a material suitable for forming the outer frame 24 and a good heat-conducting material for the surface 22 having the tips which must cool the air and bring it to the moisture separation point. Respectively one Peltier element 25 is mounted on the left and right edge of the surface 22, which elements cool the surface 22 to the desired temperature during operation. Mounted on the side of the Peltier elements 25 opposite the surface 22 in this example is a lamella 26, via which the accumulating heat is released to the surroundings. The lamellas 26 are preferably cooled by means of a separate air stream, which consists either of outside air or exhaust air and is released to the surroundings as outgoing air. In this example, the lamellas 26 therefore form the cooling elements 14 (FIG. 4). This embodiment is additionally suitable for combining the sawtooth plate 19 with the frame 10 (FIG. 8) to form a single component, by configuring the frame 24 accordingly. The same design is also applied to the other sawtooth plates 18, 20, 21 (FIG. 8) so that the module 8 can be formed by continuously stringing together such sawtooth plates 18 to 21 without interposed frames 10. This design affords two important advantages since good heat-conducting material is only used where it is needed and since the temperature of each sawtooth plate can be regulated individually because each sawtooth plate is assigned its own Peltier elements 25. The thermal conductivity of the surface 22 can be increased by mounting at least one heat pipe 27 on the surface 22. (A heat pipe is also called Wärmerohr in German). Likewise, the thermal conductivity of the lamellas 26 can be increased by means of at least one heat pipe 28. In this example, the lamellas 26 form the cooling elements 14 (FIG. 4).

The perforated plates 11, 12 (FIG. 5) can be constructed in a similar manner to the sawtooth plate 19 described with reference to FIG. 10, so that individual Peltier elements are also assigned to each perforated plate.

If the modules 7 and 8 are assembled to form a device, as shown for one example in FIG. 4, the individual channels of the modules 7 and 8 together then form the air channel for the air stream to be dehumidified. The device according to the invention further comprises a control unit 29 for controlling the Peltier elements 13 of the modules 7 and 8 and at least one sensor 30, which measures the temperature T and/or the humidity, preferably the relative humidity phi of the air. FIG. 11 shows a circuit diagram of this control unit. The output signal or the output signals of the at least one sensor 30 are supplied to the control unit 29 and used for control of the Peltier elements 13 of the modules 7 and 8. In the example, the control unit 29 comprises a first controller 31 for controlling the Peltier elements 13 of the module 7 of the zone 4 and a second controller 32 for controlling the Peltier elements 13 of the modules 8 of the zone 5. The control of the temperatures of the modules 7, 8 of the two zones 4 and 5 is complex. The basic principles of the control are explained hereinafter.

Such a sensor 30 is placed, for example, at the inlet of the air channel and measures the temperature T and the relative humidity phi of the air stream to be dehumidified. The sensor 30 can, however, also be placed at another suitable position, for example, as shown in FIG. 4 between the two zones 4 and 5. The control unit calculates the relevant dew point temperature T_(p1) from the measured values of T and phi, for example, using Equation (1) or by reference to the Mollier diagram (FIG. 2), which is stored in the control unit 29, for example, as a function, curve family, or table. The controller 31 regulates the current flowing through the Peltier elements 13 of the modules 7 of the zone 4 in such a manner that at least the perforated plate located nearest to the outlet of the zone 4 is cooled to the temperature T₁, wherein the temperature T₁ is either the calculated dew point temperature T_(p1) or a temperature a small amount higher than the dew point temperature T_(p1). The temperature T₁ is advantageously selected so that no condensed water accumulates in zone 4 and/or condensate eventually formed evaporates again in the air stream. The relative humidity of the air stream at the inlet of the zone 5 is now at least approximately 100%.

In zone 5 moisture is removed from the air stream. The water content and therefore the relative humidity of the air stream decrease. The dew point temperature varies along zone 5; at the outlet of zone 5 this temperature is lower than at the inlet of zone 5. In order that moisture can be condensed from the air stream in the form of water, the temperature of the sawtooth plates at any point in zone 5 must be lower than the local dew point temperature.

On leaving, the dehumidified air stream should have a predetermined temperature T₂ and a predetermined relative humidity phi₂. The dew point temperature T_(p2) which the sawtooth plates of that module 8 located nearest to the outlet of the air channel must have, can be calculated by means of Equation (1) or the Mollier diagram.

The controller 32 regulates the current flowing through the Peltier elements 13 of the modules 8 of the zone 5 and possibly the zone 6 in such a manner that the temperature of the sawtooth plates of the modules 8 is lower than the local dew point temperature so that moisture contained in the air stream is separated in the form of water.

The controller 31 advantageously contains a plurality of subordinate controllers 33, the controller 32 advantageously contains a plurality of subordinate controllers 34 so that the currents flowing through the modules 7, 8 can be regulated individually.

The efficiency of a Peltier element 13 depends on various factors, in particular on the temperature difference between its warm and its cool side. The controllers 33 and the controllers 34 operate the Peltier elements of the associated modules 7, 8 preferably in the optimal working range, wherein it can well occur that only some of the modules 7, 8 are operating and that some of the modules 7, 8 are switched off.

The dew point temperature which must be reached so that moisture can be extracted from the air flowing into the device having the temperature T and the relative humidity phi can be determined by reference to the Mollier diagram shown in FIG. 2. Likewise, for each individual module 8 of the zone 5 and optionally of the zone 6 its individual dew point temperature can also be determined by reference to the Mollier diagram. 

1-8. (canceled)
 9. A device for dehumidifying an air stream comprising an air channel having an inlet through which the air to be dehumidified is supplied and an outlet through which the dehumidified air is released, the air channel divided into at least two zones, a plurality of Peltier elements for cooling the air channel, at least one sensor measuring a temperature and/or humidity of the air flowing in the air channel, and a control unit comprising at least one first and at least one second controller, the control unit configured to calculate a relevant dew point temperature from the temperature and humidity measured by the at least one sensor, the at least one first controller controlling the Peltier elements of the first zone in such a manner that the air stream at the end of the first zone is cooled to the dew point temperature or to a temperature which is higher than the dew point temperature by a small amount, and the at least one second controller controlling the Peltier elements of the second zone in such a manner that the air stream in the second zone releases moisture in the form of water.
 10. The device according to claim 9, wherein a material and/or a surface structure of walls defining the air channel are configured differently in the first zone and in the second zone.
 11. The device according to claim 9, wherein the air channel is divided into at least four zones, wherein the control unit is further configured to control a temperature in the third zone in such a manner that the air stream in the third zone releases moisture in the form of water, and wherein waste heat accumulating in the third zone is supplied to the air stream in the fourth zone.
 12. The device according to claim 10, wherein the air channel is divided into at least four zones, wherein the control unit is further configured to control a temperature in the third zone in such a manner that the air stream in the third zone releases moisture in the form of water, and wherein waste heat accumulating in the third zone is supplied to the air stream in the fourth zone.
 13. The device according to claim 11, wherein a temperature in the third zone is controlled by means of at least one Peltier element, whose cold side during operation cools the third zone and whose warm side during operation heats the fourth zone.
 14. The device according to claim 12, wherein a temperature in the third zone is controlled by means of at least one Peltier element, whose cold side during operation cools the third zone and whose warm side during operation heats the fourth zone.
 15. A method for dehumidifying an air stream comprising: making the air stream flow through at least a first zone and a second zone of an air channel, measuring a temperature and/or a humidity of the air stream, calculating a relevant dew point temperature from the measured temperature and humidity, cooling the air stream in the first zone by means of Peltier elements to such an extent that a temperature of the air stream at the end of the first zone reaches a value which corresponds to the calculated dew point temperature or is higher than the calculated dew point temperature by a small amount, and cooling the air stream in the second zone by means of Peltier elements to such an extent that water condenses.
 16. The method according to claim 15, further comprising making the air stream flow through a third zone and a fourth zone of the air channel, cooling the air stream in the third zone by means of Peltier elements to or below a local dew point temperature of the air stream so that water condenses, heating the air stream in the fourth zone by heat accumulating in the third zone.
 17. The method according to claim 16, wherein said cooling is effected by at least one Peltier element whose cold side cools walls of the air channel forming the third zone and whose warm side heats walls of the air channel forming the fourth zone.
 18. The method according to claim 15, further comprising configuring a material and/or a surface structure of walls defining the air channel differently in the first zone and in the second zone.
 19. The method according to claim 16, further comprising configuring a material and/or a surface structure of walls defining the air channel differently in the first zone and in the second zone.
 20. The method according to claim 17, further comprising configuring a material and/or a surface structure of the walls of the air channel differently in the first zone and in the second zone. 